High-pressure fuel injection systems typically employ closed-nozzle fuel injectors to inject high-pressure fuel into the combustion chambers of an engine. Each of these fuel injectors includes a nozzle member having a cylindrical bore with a nozzle supply passageway and a nozzle outlet. A needle check valve is reciprocatingly disposed within the cylindrical bore and biased toward a closed position at which the nozzle outlet is blocked. In response to an injection request, the needle check valve is selectively moved to open the nozzle outlet, thereby allowing high-pressure fuel to flow from the nozzle supply passageway into an associated combustion chamber.
During operation of the fuel injector, it may be possible for a tip portion of the nozzle member to crack, erode, or completely break away, leaving the nozzle outlet continuously open to some degree. In order to ensure the high-pressure fuel is not constantly pumped into the combustion chamber of the engine, some high-pressure fuel injection systems employ a leak limiter to limit fuel leakage through the nozzle member during an injector failure.
Existing leak limiters are configured to block fuel flow to the tip portion of a leaking injector after failure of the injector. Although effective, upon shutdown of the engine, existing leak limiters reset and, during restart of the engine, fuel is once again continuously pumped through the leaking injector into the combustion chamber. In some instances, the leakage could be so significant that pressure cannot build within the fuel system during restart, thereby inhibiting further operation of the engine. If unaccounted for, this situation could leave a machine stranded and/or inhibit diagnosis of the leaking injector.
One leak limiter configured to permanently inhibit fuel leakage through a failed injector is described in U.S. Patent Publication No. 2006/0191515 (the '515 publication) by Savage, Jr. et al. published Aug. 31, 2006. The '515 publication discloses a fuel injector having a needle valve member disposed within and supported by a tip portion of a nozzle member. During normal operation, the needle valve member is moved away from the tip portion of the nozzle member to allow pressurized fuel to exit the fuel injector by way of a nozzle outlet located at the tip portion. Upon breakage of the tip portion, the needle valve member is no longer supported and descends into the nozzle member under the bias of a spring until an outer conical seating surface of the needle valve member engages an inner conical seating surface of the nozzle member, thereby isolating the outlet at the tip portion from pressurized fuel. Geometry of the needle valve member inhibits further movement that would re-communicate the outlet at the tip portion of the nozzle member with the pressurized fuel, even during subsequent intentional injection events and during engine restart.
Although the leak limiter of the '515 patent may permanently inhibit fuel leakage of a failed injector after the tip end of the nozzle member has broken away, it may still be sub-optimal. That is, during some fuel injector failure modes, for example cracking or erosion, the tip portion may not break away enough for the needle check valve to sufficiently descend and completely block undesired fuel leakage through the nozzle member. In these situations, some fuel leakage may still occur.
The fuel leak limiter of the present disclosure solves one or more of the problems set forth above and/or other problems of the prior art.